Shocking new footage has revealed just how close a massive crack, now wider in parts than the Empire State Building, is 'close' to falling off the Larsen C Ice Shelf and creating a huge iceberg.

Experts are concerned the huge calving event, which would create an iceberg with an area of more than 5,000 km², roughly the size of Delaware or Wales, could leave the entire shelf unstable.

This, they warn, could contribute dramatically to sea level rise.

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The massive crack, now wider in parts than the Empire State Building, would create an iceberg with an area roughly the size of Delare or Wales, could leave the entire shelf unstable, scientists fear. Researchers from the UK-based MIDAS project, led by Swansea University, shot this footage as they flew over the ice shelf on their way to collect science equipment

RECORD ICEBERGS

The largest icebergs known have all calved from ice shelves.

In 1956, a huge iceberg of roughly 32,000 km² – bigger than Belgium – was spotted in the Ross Sea by a US Navy icebreaker.

However, since there were no satellites in orbit at this point, its exact size was not verified. In 1986, a section of the Filchner ice shelf roughly the size of Wales calved – but this iceberg broke into three pieces almost immediately.

The largest iceberg recorded by satellites calved from the Ross ice shelf in 2001, and was roughly the size of Jamaica at 11,000 km².

'Iceberg calving is a normal part of the glacier life cycle, and there is every chance that Larsen C will remain stable and this ice will regrow,' said Dr Paul Holland, ice and ocean modeller at British Antarctic Survey.

'However, it is also possible that this iceberg calving will leave Larsen C in an unstable configuration.

'If that happens, further iceberg calving could cause a retreat of Larsen C. We won't be able to tell whether Larsen C is unstable until the iceberg has calved and we are able to understand the behaviour of the remaining ice.

'The stability of ice shelves is important because they resist the flow of the grounded ice inland.

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BAS scientists are involved in a long-running research programme to monitor ice shelves to understand the causes and implications of the rapid changes observed in the region, and shot the footage as they flew over the ice shelf on their way to collect science equipment.

During the current Antarctic field season, a glaciology research team has been on Larsen C using seismic techniques to survey the seafloor beneath the ice shelf.

Because a break up looks likely the team did not set up camp on the ice as usual.

Instead they made one-off trips by twin otter aircraft supported from the UK's Rothera Research Station.

Ice shelves in normal situations produce an iceberg every few decades.

There is not enough information to know whether the expected calving event on Larsen C is an effect of climate change or not, although there is good scientific evidence that climate change has caused thinning of the ice shelf.

Once the iceberg has calved, the big question is whether Larsen C will start to retreat.

An ice shelf is a floating extension of land-based glaciers which flow into the ocean. Because they already float in the ocean, their melting does not directly contribute to sea-level rise.

However, ice shelves act as buttresses holding back glaciers flowing down to the coast.

Larsen A and B ice shelves, which were situated further north on the Antarctic Peninsula, collapsed in 1995 and 2002, respectively.

This time-lapse image below shows the rift gradually widening from late 2014 to January of this year, adding to an 11 mile advance spotted by researchers in September. The team studying the crack say it is now inevitable it will break off, leaving a massive iceberg.

This resulted in the dramatic acceleration of glaciers behind them, with larger volumes of ice entering the ocean and contributing to sea-level rise.

Elsewhere in the Antarctic, shocking new satellite image has revealed the march of a giant crack dubbed the 'Halloween crack'.

Taken by the European Space Agency's Copernicus programme, which is aimed at Earth Observation, the data was instrumental in the recent decision to temporarily close down the British Halley VI research station in Antarctica.

The crack is located on the Brunt Ice Shelf - a floating ice sheet that moves steadily towards the ocean where it occasionally calves - when chunks of ice break off glaciers to make an iceberg.

The crack first appeared last October, when the Halley VI base of the British Antarctic Survey was only 17km from it.

Information from two satellites - Sentinel-1 and Sentinel-2, were used to monitor the crack's development.

A company called Enveo, which uses satellite data to monitor to study the frozen parts of the world, also helped with the observations.

The rift from space, showing a 900 foot crack that has emerged - and is growing at an alarming rate. In late December, the rupture had already extended by 11 miles (18km), leaving the future iceberg connected along only a small fraction of its length.

A crack in Antarctica that is more than 100 miles (160km) long has grown by another 6 miles (9.6km) in just over two weeks. This adds to the 11 miles (17km) advance in September, creating a 17 mile (27km) total increase in less than a month

In November and December, the crack was growing in length by as much as 600 metres per day.

While the Halley Research station had to move because of this, it was designed to be relocated if the ice becomes dangerous.

The station already had to relocate 23km inland during Antarctica's last summer months because of another chasm (crack) which had lain dormant for more than three decades but became active again in 2013.

The crack appeared last October, when the Halley VI base of the British Antarctic Survey was only 17km from the crack

Dr Hilmar Gudmundsson, the survey's lead scientist, said: 'The frequency of Sentinel-2 images and Sentinel-1 radar products allows us to follow in detail and almost in real time the development of the crack as it grows week by week.'

The two Sentinel satellites are being used to monitor three cracks - the Halloween crack, which is now growing at 200 metres per day, and two other ice chasms.

The satellites are also being used to detect any new cracks that may arise.

Images of the Halloween crack generated by The Sentinel-1A and Sentinel-1B satellites. The crack is located on the Brunt Ice Shelf - a floating ice sheet that moves steadily towards the ocean where it occasionally calves - when chunks of ice break off glaciers to make an iceberg

The Halley VI Research Station was forced to close its Antarctic research base amid rising fears it could fall into a huge ice chasm. Shocking new drone footage shows just how massive the growing crack in the ice is

The Sentinel-2 satellite has been programmed so that it takes images every time it flies over the cracks so that there's a maximum chances of photos without clouds in them.

Other satellites, Sentinel 1-A and Sentinel 1-B, have also been recording data with two crossing tracks.

This allows researchers to map the growing rift and, showing how the ice shelf is deforming at the tip of the growing crack.

Dr Mark Drinkwater, head of ESA's Earth observation mission, said: 'Routine Antarctic summer observations by the combination of Copernicus Sentinel-2A and Sentinel-1A and -1B are now demonstrating their value for monitoring rapid environmental change and providing information crucial to informed decisions on matters of safety and security in Antarctica.'

'Though without direct effect on Antarctic infrastructure, similarly dramatic summer development of ice-shelf fractures is revealed around Antarctica, notably Pine Island glacier in West Antarctica and the Larsen-C and Brunt ice shelves in the Weddell Sea.'

Antarctica will soon be facing the dark winter months, and the Sentinel-1 satellite will continue to provide images so that thes changes can be monitored.

KILLER CHASMS

The first chasm, which had lain dormant for more than three decades, became active again in 2013. Since them, the crack has lengthened at a rate of 1.7 km per year.

On October 2016, a second crack appeared some 17 km to the north of the research station.

Researchers conclude that they are unable to predict with certainty what will happen to the ice shelf during the forthcoming Antarctic winter and beyond.

The Halley VI Research Station was relocated 14 miles across the Brunt Ice Shelf, amid fears in could slide into an encroaching fissure in the ice shelf. This map shows the current location of the original crack that forced the research station to relocate, labelled as Chasm 1